Fig. 2: Replication kinetics and fusogenicity of SARS-CoV-2 recombinant viruses in lung cell lines.
From: Phenotypic evolution of SARS-CoV-2 spike during the COVID-19 pandemic
a,b, Replication kinetics of pre-Omicron (a) and post-Omicron (b) viruses in Calu-3 cells. Cells were infected with equal viral genome copies of each virus and the amount of virus released in the supernatant was quantified by RT–qPCR at different timepoints post infection (hpi) as indicated. Recombinant viruses were assessed across distinct experiments with S:B.1 used as reference virus in each experiment (indicated as a light grey area). Note that values at time 0 reflect the titres of input virus, while those at 1 hpi are the titres of residual virus in the supernatant after 1 h infection and one wash of the monolayer. c, Heat maps of viral titres relative to S:B.1 for all viruses expressed as log2(fold change) at each indicated timepoint. d,e, Live virus-based fusion assay in AAT-GFP10/AAT-GFP11 cells. The fusion activity was measured over time and expressed as a percentage of maximum fluorescence over S:B.1; pre-Omicron (d) and post-Omicron (e) recombinant viruses. For a, b, d and e, the light grey area indicates the data relative to the reference virus S:B.1 in all experiments. Data are represented as mean ± s.e.m. of 3 independent experiments each performed in triplicate. Statistical significance of differences between S:B.1 and the other viruses across timepoints was determined using one-way analysis of variance (ANOVA) with multiple comparisons between area under the curve using the Holm–ŠĂdák post hoc test. For c, statistical significance of differences between S:B.1 and the other spike-bearing viruses at each timepoint (heat maps on the right) was instead determined by one-sample t-test. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001. f, Heat maps as percentage of maximum fusion over S:B.1 at indicated timepoints. For f, statistical significance of differences between S:B.1 and the other viruses across timepoints was determined using two-way ANOVA with multiple comparisons between area under the curve using the Holm–ŠĂdák post hoc test. The calculated P values are indicated in the figures.
